The invention relates to a pressurised medium delivery device, consisting of a pump with a suction pipe, at least one pressure pipe and a pressurised medium supply container which is filled at least partially with a quantity of pressurised medium.
Pressurised medium delivery devices of the type mentioned here are known from various applications. They have a pump which sucks up through a suction pipe which projects into the supply reservoirxe2x80x94and generally through a filter devicexe2x80x94a pressurised medium such as hydraulic oil from a pressurised medium supply and supplies this pressurised medium through a pressure pipe to a consumer.
The pump is generally mounted above the oil sump. It sucks up oil from the oil sump through the filter and serves as the pressure and volume flow supplier for hydraulic or electro-hydraulic control systems. These controls contain slide valves which slide with play in bores, with the play providing gaps which are indeed narrow but allow the hydraulic oil to pass through. Generally the controls are located at least in part above the oil sump so that when switching off the system the control can slowly empty and air penetrates into the ducts. Thus in the end the suction pipe of the pump can be emptied by air flowing back from the control into the pressure pipe through the pressure pipe/pump/suction pipe route and where applicable filter. This has the result that particularly when starting up the pump when the oil is cold the pump first has to expel the air from the suction pipe. As a result of the high elasticity of air it takes a relatively long time until the pump can build up through its delivery capacity a corresponding vacuum to suck the oil up through the filter. This causes a correspondingly long time delay for the build-up of pressure. Furthermore by sucking up an air-oil mixture with a very high proportion of air a lot of starting noise may arise.
On the other hand systems are known which avoid an emptying of the suction system by using a non-return valve on the suction pipe or in the pressure pipe. The drawback here is the higher suction resistance or through-flow resistance which arises, particularly when cold, which leads to pressure losses and thus to a lower delivery or greater power consumption of the pump. Furthermore with a non-return valve the functional reliability is very quickly impaired, e.g. through dirt at the sealing points, so that air can penetrate into the system and the intake tract thereby runs empty.
Systems are also known wherein the pump was placed with the intake pipe directly and completely underneath the oil surface in the sump, or at least the intake pipe is made extremely short. This is however often not possible through reasons of space.
It is therefore the object of the invention to provide a pressurised medium delivery device of the type mentioned above which does not have these drawbacks and which is improved compared with the aforesaid measures.
This is achieved through a pressurised medium delivery device having a pump, suction pipe, at least one pressure pipe and pressurised medium supply volume in a pressurised medium supply container.
The pressurised medium delivery device according to the invention is characterised in that the first openings of the suction and pressure pipe remote from the pump are arranged below the surface of the pressurised medium of the pressurised medium supply and project at least when the system is stationary below this surface.
Furthermore the pressurised medium delivery device is characterised in that the at least one pressure pipe has a part which is connected to the pump and is mounted above the surface of the pressurised medium supply volume in the pressurised medium supply container, and has a further part which is mounted at least in part below the surface of the pressurised medium supply volume.
According to the invention the part of the at least one pressure pipe below the surface of the pressurised medium supply volume has a connection with the pressurised medium in the pressurised medium supply volume.
In a preferred embodiment of the invention at least one pressure pipe, leading from the pump, is mounted at least over a part of its extension below the surface of the pressurised medium supply volume and where applicable then leads out again beyond the surface.
A pressurised medium delivery device is particularly preferred where the pressurised medium region inside the pump, the suction pipe and the partial region above the surface of the pressurised medium supply volume of the at least one pressure pipe has no opening for a pressurised medium outflow.
According to the invention the at least one pressure pipe only continues to the pressurised medium consumer after projecting under the surface of the pressurised medium supply volume.
One embodiment is preferred where the at least one pressure pipe has below the surface of the pressurised medium supply volume connecting means to provide a fluid connection with the pressurised medium.
According to the invention a pressurised medium connection between the pressurised medium in the pressure pipe and the pressurised medium in the pressurised medium supply volume can be produced by means of the connecting means.
In a preferred embodiment the pressurised medium connection can be interrupted or switched off.
In a further preferred embodiment, the at least one pressure pipe leads to at least one pressurised medium consumer after the connecting means of the at least one pressure pipe, seen in the flow direction.
According to the invention the connecting means represent a pressurised medium resistance opening.
In a preferred embodiment the resistance is represented by at least one leakage gap of a valve device.
According to the invention the connecting means represents a closable resistance.
An embodiment is preferred wherein the resistance opens with flow in one pressurised medium flow direction and closes in an opposite pressurised medium flow direction.
According to the invention in a further embodiment the resistance closes with flow in the flow direction from the pressure pipe to the supply quantity and opens with flow in the flow direction from the supply quantity to the pressure pipe.
In another design according to the invention the resistance is open in the event of flows in both directions.
An embodiment is preferred where the resistance is a non-return valve.
In a further embodiment the non-return valve is a leaf spring or spring tongue or plate valve.
In another design according to the invention the non-return valve is a ball or cone seat valve.
In another preferred design the non-return valve is a slide valve.
According to the invention the non-return valve closes through spring force and/or weighting and opens through compression force.
Particularly preferred is the design with a pump, with a suction pipe, with at least one pressure pipe, a pressurised medium supply volume and a pressurised medium container wherein these are arranged in relation to the surface of the pressurised medium supply so that they represent a system of xe2x80x9ccommunicating pipesxe2x80x9d in their method of operation.
Furthermore a pressurised medium delivery device is preferred, more particularly with a pump, with a suction pipe, with at least one pressure pipe, a pressurised medium supply volume and a pressurised medium container wherein these are arranged in relation to the surface of the pressurised medium supply so that the geodetic pressure is balanced in this region within the pressurised medium.
In another pressurised medium delivery device according to the invention, more particularly with a pump, with a suction pipe, with at least one pressure pipe, a pressurised medium supply volume and a pressurised medium container, these are arranged relative to the surface of the pressurised medium supply so that (in their method of operation) the intake area is prevented from running empty (at least when the vehicle is stationary).
In a particularly preferred embodiment the device is arranged in relation to the surface of the pressurised medium supply so that the intake area is prevented from running empty even if the control is idling at least in part.
According to the invention the device is arranged in relation to the pressurised medium supply surface so that the intake area is prevented from running empty even without a non-return valve in the intake region and/or pressure region.